In the past, when it was desired to increase the capacity of the grain tank of an agricultural harvesting machine such as a combine, a rigid walled structure was sometimes, if not typically, affixed around an upwardly facing opening of the grain tank so as to extend upwardly therefrom. Such known extensions generally provided satisfactory grain capacity increasing utility, but suffered from various shortcomings. Due to the increase in overall height of the combines when such structures were installed, the height of the combine often exceeded government imposed height limitations for road travel, as a consequence of which removal and reinstallation of such structures was often necessary, with attendant expenditures of time and efforts. Additionally, such rigid structures themselves provided no covering protection for the grain tank and its contents.
It was also known to provide an extendible cover for the upwardly facing opening of a grain tank, which cover was automatically movable directly upwardly from the periphery of the opening along at least two sides of the grain tank so as to expand the grain holding capacity. However, since at least two sides of such known devices extended only directly upwardly, and not outwardly, from the upward opening, the increased grain holding capacity was more limited than was desirable.
More recently, a foldable grain tank extension for combines was developed, as disclosed in U.S. Pat. No. 6,679,772. Such construction was a significant advance, but did not fully address the protection of the grain tank from introduction of rain and foreign materials when the grain tank extension construction is folded or difficulties experienced with the use and serviceability of linear actuators or other linkages mounted interior to the grain tank to control the unfolding of the grain tank extension panel construction. There has thus remained a desire for a foldable grain tank extension that can not only secure the advantages provided by the construction of U.S. Pat. No. 6,679,772 but which would also enable the grain tank to be protected from the introduction of rain and foreign materials when the construction is folded and would permit servicing of at least major portions of the linkages and their systems even while the grain tank is full.